What is Detergents?
The common soap (sodium salt of fatty acid) is one of the oldest detergents but it is relatively weak. Synthetic detergents are stronger than soap and give lather even in hard water.
The common soap (sodium salt of fatty acid) is one of the oldest detergents but it is relatively weak. Synthetic detergents are stronger than soap and give lather even in hard water.
Dialysis is a process of separating dissolved substances from a solution using a semi-permeable membrane which allows only some dissolved substances to pass through. Many substances such as cell walls and cellophane act as semi-permeable membranes.
Dialysis is used to remove waste-products from the blood of patients with impaired kidney function. Accumulation of waste products especially urea, in the blood can prove fatal.
Dialysis of blood is carried out using a dialysis machine. Blood drawn from the artery in the forearm of the patient is passed through a semi-permeable membrane. The tubing is placed in a solution called dialysis fluid. Since the blood has a high concentration of impurities compared to the dialysis fluid, a concentration gradient builds up. This results in a flow of soluble impurities from the blood into the dialysis fluid. This continues till the concentrations on each side of the membrane are balanced. To prevent clotting of blood in the dialysis machine, the anti-clotting substance heparin is used.
The most commonly used atoms and molecules in atomic clocks include caesium atoms, hydrogen atoms and molecules of ammonia gas. Atomic clocks based on rubidium atoms instead of caesium are now in use. Some atomic clocks gain or lose no more than a second in 200,000 years. These are used to keep time in laboratories and observatories.
For obtaining a sample a hollow needle is carefully inserted under local anaesthesia through the expectant mother’s abdomen. The amount of fluid withdrawn is only about 20 ml. This fluid contains cells from the developing baby. Chemical and microscopic examinations of these cells can provide invaluable information, revealing the presence or absence of genetic disorders which cannot be detected otherwise.
The chromosome analysis of the cells in the amniotic fluid can also reveal the sex of the baby.
Allergy is a state of hypersensitivity acquired through the exposure to a particular substance, called allergen. Spores, pollen, cat’s hair and proteins of egg, milk, and fish are some common allergens. The most common allergen is the house-dust mite.
Usually only parts of the body which are exposed to allergens show signs of allergy in the form of rashes or weals. However, if an allergen gets into the blood stream, it can cause reactions almost anywhere in the body.
Practically all allergies are caused by an over-reaction of the body’s defence mechanism when white blood cells react with allergens considering them as dangerous infectious organisms, it leads to allergy. Under normal conditions, the white blood cells (lymphocytes) on coming in contact with foreign substances like bacteria, viruses and proteinaceous matter produce what are called antibodies. The antibodies combine with the foreign substance and neutralize it. But when an antibody is formed against a harmless protein it attaches itself to mast cells which contain chemical— histamine. When the particular protein enters the body again, histamine is released. Due to the action of histamine blood capillaries are dilated, their walls become leaky and fluid from the blood comes out in the nearby tissues and they swell. The characteristic redness and itching in an allergy is due to dilation of blood capillaries.
HIV spreads from an infected person to a healthy person through body fluids. Sexual transmission of HIV is most common. Contaminated blood and blood products besides passage of the virus from infected mother to unborn baby are other ways by which the virus spreads.
It is a phenomenon caused by industrial pollution. Natural rain always contains a small amount of dissolved carbon dioxide which makes it slightly acidic. But large-scale burning of coal or oil in industries, power plants and vehicles produce large amounts of gases such as sulphur dioxide, nitrogen oxides, etc., which are released into the atmosphere. These gases rise up with air currents and may be carried by prevailing winds many hundred of kilometres away from their source. Under favourable conditions they react with water vapour and oxygen in the atmosphere to produce sulphuric and nitric acids which eventually come down with rain, snow or fog. Compared to a pH of around 6 for normal rain, acid rains cause considerable damage to vegetation, trees and marine life. As the gases retry and acid rains fall in another damaging its flora and marine life, it has become a cause of concern to all countries. The countries worst affected by acid rains are southern Sweden, Norway, parts of central Europe and eastern regions of North America. Most European countries are therefore making efforts to reduce sulphur emissions by their industries and power plants.
Plants have special structures called root hairs for absorbing water and other nutrients from the soil. The root-hairs are thin-walled extensions of the outer layer of cells in the root. Deep underground they are surrounded by solutions of various minerals and nutrients in the moist soil. Some of these nutrients such as the nitrogen compounds simply pass through the root-walls when they are present in high concentrations in the soil. The process can be likened to the natural flow of water from the high hills to low valleys. Other nutrients such as minerals which are present in lesser quantities in the soil than inside the cells are transported into the root hairs by special proteins located on the cell-walls, a process which can be likened to pumping of water from wells to tanks higher up.
In addition to this, during the growing season, a tree passes tonnes of water into the atmosphere from its leaves through transpiration.
This creates a partial vacuum that is quickly filled by the water being pushed up from the roots. Water molecules stick together, and as water is lost during transpiration, this cohesion causes a chain reaction that is transmitted all the way down.